The poem apparently originally appeared in Collected Poems of Vagaland by T. A. Robertson (Lerwick: Shetland Times, 1975).

The poem has apparently been reprinted in The Windswept Isles: Shetland and Its People by Elizabeth Balneaves (London: Gifford, 1977), page 274; but, since the book is still under copyright, only "snippets" are viewable online. However, I was able to extract this much:

Oot bewast da Horn o Papa
Rowin Foula doon!
Ower a hidden piece o watter
Rowin Foula doon!
Roond da boat da tide-lumps makkin
Sunlicht trowe da clouds is brakkin;
We maan geng whaar fish is takkin,
Rowin Foula doon.

Fishy knots wir boat haes truly
Nae misforen knot.
We hae towes and bowes and cappies,
Ballast i da shott,
Paets fir fire i da kyettle,
Taaties fir da pot.

Laek a lass at's hoidin, lachin,
Coortit be her vooers,
Papa sometimes lies in Simmet
Veiled wi ask an shooers;
Dan upo da wilsom watter
Comes da scent o flooers.

We can bide ashore nae langer ?
We maun geng an try.
We'll win back boys, if we soodna
Scrime da moder-dye,
Fir da scent o flooers in Papa
Leds wis aa da wye.

[It isn't clear to me whether I have the complete poem. The poem is apparently written in the Shetland dialect. The McCalmans apparently toned down the dialect somewhat.]